Oh, strange, normally the ones that say "saltwater" should be able to measure close upto 50 ppt (parts per thousand). For reference average Ocean Water is 35 ppt.
The one I got is supposed to be able to be use for drinking water, in additions to saltwater tanks.
Here is the link: https://www.amazon.com/gp/product/B0885YXFJ6/ref=ppx_yo_dt_b_asin_title_o05_s01?ie=UTF8&psc=1